More than a year into the COVID-19 pandemic, SARS-CoV-2 antibody tests are plentiful, but highly accurate, affordable, point-of-care versions with quantitative data still don’t exist. An innovative test from scientists at the University of California, San Francisco, and colleagues could change that.
To develop their assay, the researchers fused fragments of a luminescent enzyme to SARS-CoV-2 viral protein antigens—specifically the S-protein receptor binding domain or the N-protein terminal sequence. The engineered antigens glow when they react with antibodies against them, resulting in luminescent biosensors that are compatible with a commercially available handheld luminometer.
The assay quantifies antibody levels within 30 minutes. The researchers evaluated it with 159 serum and plasma samples from 3 COVID-19 cohorts including inpatients, outpatients, and recovering patients. Its sensitivity was 89% for detecting anti–S-protein antibodies and 98% for anti–N-protein antibodies, and its specificity was more than 99% for both. Additional testing also demonstrated the assay’s potential for use with whole blood from simple finger sticks or saliva samples (with somewhat less accuracy), valuable in low-resource settings.